Even though equipment has been previously proposed for inserting tubes into heat exchangers, the operation is still performed almost entirely by hand. An important reason for this is the fragility of the tubing which, because it may have a relatively thin wall, can be easily bent or distorted. This is particularly troublesome when holes in the tube sheet or baffles of the heat exchanger are not in perfect alignment or have imperfections or foreign material on their edges which is often the case. Thus, the laborious hand insertion method that has been used for decades is still employed. Typically, one man is spaced about every ten feet along the length of a tube which may be over 40' long. Workmen at various intervals remove tubes from a shipping box, place them near the tube sheet of the heat exchanger and attach pilots. Working in unison, the men pick up the tube, hold it level with the tube sheet hole and walk the tube into the condenser. Any deviation from a straight line may cause the tube to choke or bind since the holes allow only a small amount of clearance (about 0.006 inches) for the tube. Automated equipment has been proposed For example, U.S. Pat. No. 4,104,790 describes a pipe installing apparatus wherein four pipes are simultaneously engaged by two cooperating rollers placed above and below the pipes. No provision is made for helping to prevent the tubes from buckling, bending or becoming distorted during the insertion process as may happen, for example, when the tube encounters an obstruction such as a piece of foreign material on the edge of one or more of the openings through which the tube is passed and no provision is made to cause the tube to extend the proper distance, e.g., 1/4", for flaring the end and/or sealing it to the tube sheet. Similarly, U.S. Pat. No. 4,221,534 describes a device for feeding tubes into a heat exchanger which includes a pair of friction wheels for forcing the tubes through openings in the condenser. Again, there is no provision for relieving stresses in the tube as it passes through the maze of perforated baffles. Accordingly, in some situations, there is a tendency for pressures to build up and for the tube to become distorted, bent or otherwise damaged in the insertion process. Moreover, no provision is made for clearing the baffle openings prior to the insertion of the tube nor for allowing the rear end of the tube to project a fraction of an inch from the condenser following insertion.
In view of these and other deficiencies of the prior art, it is an objective of the present invention to provide an improved tube insertion method and apparatus capable of efficiently and dependably inserting a tube measuring 1".times.46' at the rate of about two per minute with the proper extension (end stock) following insertion with an effective provision for reducing distortion, bending or related damage to the tubing as it is inserted. A further object is to provide an improved tube insertion method and apparatus wherein a tube can be inserted by a single operator wherein highly skilled labor is not required. A further objective is to provide means for aligning the insertion apparatus with the tube when the leading end of the tube has been placed manually in the heat exchanger. Further objectives include the provision of a simple apparatus that can be manufactured at low cost, is rugged in construction, reliable in operation and unlikely to require maintenance and repair, but which can easily be maintained during use, can be adapted to accept pneumatic, hydraulic or electric power, wherein the speed of insertion can be varied and driving force on the tube can be changed to provide a light or heavy thrust.